1. Field of the Invention
The present invention relates to an information recording and/or reproducing apparatus having a processor and its method for recording and/or reproducing information to/from a magnetic disk, a magnetooptic disk, or the like in response to a command of a computer by connecting the apparatus to a computer.
2. Related Background Art
Hitherto, as a secondary memory apparatus of a host computer, a magnetic disk apparatus, a magnetooptic disk apparatus, or the like is used. The host computer and the secondary memory apparatus are connected by an interface such as an SCSI (Small Computer System Interface) or the like. In such an interface, generally, a read command, a write command, or the like is generated from the host computer to the apparatus and the host computer can recognize the end of execution of the command by a notification from the apparatus.
The operation of the apparatus side will now be described as an example with respect to a magnetooptic disk apparatus of 3.5 inches connected to the host computer by the SCSI. It is assumed that the magnetooptic disk apparatus uses a disk according to the international standard ISO 10090.
FIG. 1 shows the operation of the magnetooptic disk apparatus when a read/write command is received from the host computer. First, when a CPU, which is provided in the magnetooptic disk apparatus and executes a command process receives a command, the CPU analyzes the command in step S1. In this instance, the CPU discriminates the kind (read, write, etc.) of command, disk position, data size, and the like. On the basis of the result of the discrimination, an address on the disk to be read or written is calculated. The disk position designated by an SCSI command by the host computer is a logical position and its address is expressed by a serial number. On the other hand, the disk address specified by the ISO 10090 is a physical address and is expressed by a track number and a sector number. A defective sector and an alternate sector to relieve the defect are provided in the disk. Alternation management information to manage those sectors and the like have also previously been recorded on the disk. When converting from the logical address designated by the SCSI to the physical address of the disk, it is necessary to also check the presence or absence of the defective sector or the like. When the physical address of the disk is determined, a recording and reproducing head is moved to the physical address (such an operation is called a seek) in step S3. The reading or writing operation is executed for the disk in step S4. After the reading/writing operation is executed, the execution result is sent as a status to the host computer in step S5. In this way, one command process is finished.
In the magnetooptic disk apparatus, not only is the above execution of the command process stationarily performed, but also the controls of various drives are stationarily executed. For example, there are executed: a speed control of a spindle motor to rotate the disk; and output control of a laser beam for recording and reproducing; tracking/focusing servo controls for positioning the recording/reproducing head; and the like. Those various kinds of drive controls are digitally processed by a high speed CPU from a viewpoint of the superiority of the costs, performance, and the like. A construction such that the CPU executes the command process and the CPU controls various drives in order to reduce the costs has also been proposed. In this case, since it is necessary to always perform the control during the driving operation, for example, the driving process is interrupted and the command process is performed at a predetermined interval.
The recent improvement of the performance of the computer is remarkable and an increase in processing speed of a secondary memory apparatus of the computer is also demanded in association with it. Namely, it is demanded to reduce the command executing time. The command executing time includes not only an actual operation (seeking operation of the head, recording and reproducing operations of data, and the like) time for the actual reading/writing operations and the like of the drive but also a command pre-processing time which is required for the drive to analyze the command from the host computer (step S1 in FIG. 1) and to calculate the target address (S2 in FIG. 1) and a command post-processing time which is required to notify the result of the operation to the host computer (S5 in FIG. 1) after completion of the actual occupation such as reading, writing, or the like. In order to reduce the command executing time, not only is a decrease in actual operating time of the drive demanded, but also a decrease in command pre-processing and command post-processing time are demanded.